Beam switch for single trace observance



March 30, 1948. c PUCKETTE, JR 2,438,717

BEAM SWITCH FOR SINGLE TRACE OBSERVANCE Filed May 28, 1943 giw; 22m

Patented Mar. 30, 1948 BEAM svvrron FORsiNGLE trance" 7 *OBSERVANCE Gharles Puckette,. .r., Bidgewoo'd; N. zLpassigno'r to Allen B. .Du-Mont Laboratorieaalnc .-Passaic,- N. 1., a corporation of Delaware 7 1943 jSer-ialNo assess I Application May 28, screams. (c1. sis-22) This invention relates to a'device by which the cathode-ray or beam of an oscillograph can be caused tomake-asinglesweep. The b'eamiscut o'fl during its'return trace. With this invention the halo 'c'fiec't 'is prevented from occurring on the screen of an oscillograph or cathode-ray tube when the residual trace of the beam is being observed, for example, on a tube that has a long persistence screen.

With this invention a longer efiective observing time of the residual trace is provided and less distraction is caused by the halo effect than has heretofore been the case.

The invention is of particular use with a single sweep cathode-ray oscillograph and enables transients to be observed by a single sweep method. With this invention a single sweep trace provides its own intensity control through an electronic switch which controls a high frequency signal that is applied to the z-axis or control grid of the cathode-ray tube. The electronic switchis controlled by a local sweep circuit in such a way that both the brightness and the timing of the brightening of the trace is regulated.

The invention may be understood from the description in connection with the accompanying drawings, in which:

Fig. 1 shows a diagram of connections for carrying out the invention; and

Figs. 2, 3 and 4 are diagrams showing the operation of the device.

In the drawing, reference character I indicates a vacuum tube to the plate 2 of which a positive potential of, say, 350 volts is applied. The cathode 3 is loaded with or biased by an impedance 4, which may be a resistance, an inductance, or both, which is connected by sliding contact 5 to resistor 6 one end of which is grounded. A signal S, such as a sawtooth wave from a sawtooth generator, is applied to the grid 1 of tube l by lead 8.

A generator [0, which may be a high frequency sine wave generator, for example, is coupled by capacitor H to the control grid !2 of pentode ii The cathode I4 of this tube 13 is directly connected to the cathode 3 of tube l. potential which may be 350 volts is connected through resistor IE to the plate It of tube I3 and the screen grid I! of this tube is connected through resistor I8 to this 350 volt source. A. capacitor i9 is connected between screen grid it and ground. The plate 16 is coupled by capacitor 20 to the terminal 2| from which connection is made tothe control grid 3| of the cathoderay tube 32.

A source of Azresistance 2:5uis" locatedbetweenzresistances 6 and [8, 5a resistance.26 isrlocateii betweenegrid l2 andcont'act 5, andt resistance .2! isa-located betweenith'e-voltage regulator 28 andzthe voltage source. The zpositiveiside roiithis aegulatoriis cbnnected :at the junction 1 0i resistances x3", :25 "El-Id 2'5, and its negative si'dezto ground.

The lead 30 extends from terminal 2| to the control grid 3| of the cathode-ray tube 32 which is somewhat diagrammatically represented as a tube having a cathode 33, anodes 34 and 35, and pairs of deflecting plates 36 and 31.

The operation is as follows, with the device adapted to produce a single trace on the face 38 of the cathode-ray tube 32 so that it can be observed. The signal that produces the trace that is to be observed is applied in the known way to the y-axis deflection plates 31, and is also used to synchronize the sawtooth wave generator which generates the wave S which is applied to the x-axis plates 36 of the cathode-ray tube 32. At the same time it is applied to grid 1 of tube 1.

When no potential is applied to the grid of tube I the potential on its plate causes current through it and through resistance 4 to raise the potential of cathode 3 and cathode It to the point where no current flows through tube [3. However, when the potential of signal S decreases to the cut-off value of tube I, represented by dotted line 40 in Fig. 1 and in Fig. 2 on a larger scale, current ceases to how through tube I during the time interval cd of Fig. 2.

This causes the potential of cathode H to decrease, thus permitting the high frequency sine wave signal from source l0 which is applied to grid !2 of tube I3 to be passed by tube l3 as shown in Fig. 3, during the time interval c-d.

This wave W is coupled by condenser 20 and lead 30 to the contro1 grid 3| which is known as the z-axis of the cathode-ray tube 32. The intensity control of the cathode-ray beam of cathode-ray tube 32 is normally adjusted to cut oil in the known way when the beam is at rest, but when the signal S causes the signal from source I!) to trigger tube [3, the trace of the cathode-ray beam in tube 32 is intensified to observable brightness. The signal is cut on at the end of the sweep caused by signal S and the beam is blanked out.

The trace being observed on the face 38 of the cathode-ray tube 32 appears as a succession of dots or dashes of light, as indicated at 43 in Fig. 4, the number of them being determined by the frequency of the source I0. By the use of a long persistence screen 38 on cathode-ray tube 32, a single trace may be observed for a considerable dicated on the drawing are illustrative and may be varied considerably for difierent conditions.

What is claimed is:

1. A device for producing upon the screen of a cathode-ray tube a series of dots, which comprises a vacuum tube to the control grid of which a sawtooth wave of potential is applied, another vacuum tube having its cathode directly connected to the cathode of said flrst named vacuum tube, an adjustable resistor between the cathodes of said tubes and ground and a source of potential of higher frequency than said sawtooth wave connected to the control grid of said other vacuum tube, another resistor, a source of positive potential connected through said last named resistor to the plate of said-second named vacuum tube and to the ungrounded end of said adjustable resistor, and a condenser coupling said plate to the control grid of said cathode-ray tube.

2. Thedevice of claim 1 in which said source of positive potential is connected directly to the plate of said first named vacuum tube.

4 3. The device of claim 1 in which said source of positive potential is connected to ground through resistors in series one of which is said adjustable resistor.

CHARLES PUCKE'ITE, JR.

REFERENCES CITED The following references are of record in the file of this patent:

OTHER REFERENCES Proceed. I. R. E., vol. 30, No. 10, pp. 458-464,

October, 1942, "A portable high-frequency square-wave oscilligraph for television, by Kell et al. 

